1. Field of the Invention
The present invention relates to a continuous-length switch which is operated under the load of a human being, an animal, a substance or the like to electrically detect the existence thereof.
The present invention also relates to a continuous-length switch which is to be used for detecting contact of a substance or the like and is excellent in durability.
The present invention also relates to a method for manufacturing the switch as described above.
2. Prior Art
Conventional continuous-length switches generally have a construction in which both ends of a pair of opposed electrode plates are insulated, and one of the electrode plates, i.e. an upper electrode plate 151, for example, has been worked to have an odd-shaped geometry such that a linear portion of the electrode plate 151 is interrupted, as shown in FIG. 14, to increase sensitivity of the switch. With such a geometry of the upper electrode plate 151, the edges are not linear, but rather are interrupted, which presents the following problems.
A part of the upper electrode plate 151 may get beneath the end insulating material when heavily deformed by an external force, which results in short-circuiting of the switch, which is a fatal fault.
When a lead wire is to be drawn out, the geometry in the direction along the breadth of the switch may be varied, and drawing the lead wire out may cause the switch to be stretched like a spring, depending upon a cutting location. Therefore, a precision end working as a secondary working for prevention of this stretching may have to be provided at the drawing-out location.
With a machine tool or the like, a safety mat M which has a continuous-length switch connected in series is used to assure operator safety. In this case, a four-wire type disconnection detection circuit which uses a power supply 160, a current limiting resistor R, and a relay 161 for detecting disconnection between the upper electrode plate 151 and a lower electrode plate 152 that is opposed to the upper electrode plate, as shown in FIG. 15, is employed.
Because the upper electrode plate 151 through which a current flows is odd-shaped as shown in FIG. 15, its line length is approximately two times as long as that which would be obtained if the electrode plate were linear. Therefore, when this four-wire type disconnection detection circuit is used for carrying out disconnection detection, the electrical resistance is increased, which results in an increased power loss.
When the operator arrives on the safety mat M, a wire is disconnected, the power supply 160 fails or a coil 162 is deenergized, resulting in contacts 161a for the relay 161 being opened, which allows the power fed to the machine tool or the like to be shut off.
However, in this case, the four-wire type disconnection detection circuit must always be supplied with a current to energize the coil 162 for the relay 161, and therefore, a problem is presented in that the power loss due to the circuit resistance cannot be avoided.
Another conventional continuous-length switch 250 generally has a construction with which both ends of an opposed upper electrode plate 251 and lower electrode plate 252 are insulated with an insulator 255 as shown in FIG. 33 to FIG. 35. As the geometry of either one of the upper electrode plate 251 and lower electrode plate 252, i.e., the upper electrode plate 251 for example, a concave and convex geometry as shown in FIG. 36 has been adopted to enhance the sensitivity associated with some switches.
The geometry of this upper electrode plate 251 can be easily deformed if a force “f” in the direction of a tensile load is applied to the upper electrode plate. Therefore, a method which winds a string 253 around the circumferences of the upper electrode plate 251 and lower electrode plate 252, and fixes the string 253 thereto with an adhesive tape has been adopted.
However, such a continuous-length switch 250 presents problems, such as an increase in the number of manufacturing processes required, and the upper electrode plate 251 getting beneath the insulator 255 which results in a short-circuit.
Although it is not shown, an upper electrode plate with which polygonal holes are arranged at fixed intervals along a center line in the longitudinal direction of the electrode plate has been adopted.
If such an upper electrode plate is used, the need for steps of winding a string around the upper electrode plate and the lower electrode plate, and fixing the string to the electrode plates with an adhesive tape is eliminated, thereby resulting in the manufacturing process being simplified.
However, with the upper electrode plate having such a configuration, a problem is that the electrode plate can be stretched and contracted only within a small range based on its metallic elasticity when a force in the longitudinal direction is applied.
As a result of this, when this continuous-length switch is wound up for manufacturing, transporting, construction, storing, or the like, one electrode plate may be buckled and plastically deformed, resulting from the difference between the inside and outside diameters of the upper electrode plate and the lower electrode plate. Therefore, for a continuous-length switch having a long overall length, there sometimes arose the need for handling the switch without winding it up, which was inconvenient especially with regard to transporting, storing, and the like.
An example of another conventional continuous-length switch will be explained with reference to FIG. 43 and FIG. 44.
A conventional continuous-length switch as shown in FIG. 43 and FIG. 44 comprises a lower electrode plate 321 made of a continuous-length plate-like conductive material; an upper electrode plate 322 made of a continuous-length plate-like conductive material; and a jacket 324 made of a continuous-length insulating material which has a pair of symmetrical protrusions 324a and 324b on the inner walls of both sides thereof to form a space portion 323 between the lower electrode plate 321 and the upper electrode plate 322, and is open on its bottom side; two strings 325, for example, which are wound around the circumference of the jacket 324 in a crossed configuration to integrate the lower electrode plate 321 with the upper electrode plate 322; and a continuous-length adhesive tape 326 which is bonded to the strings 325 on the bottom side of the lower electrode plate 321 along the longitudinal direction of the lower electrode plate 321.
In other words, the upper electrode plate 322 is held between the pair of protrusions 324a and 324b inside the jacket 324 and an inner wall ceiling 324c of the jacket 324; and the lower electrode plate 321 is attached to the lower surfaces of the pair of protrusions 324a and 324b. Then, the process of cross-winding the two strings 325 is carried out to integrate the lower electrode plate 321 with the upper electrode plate 322.
At the middle of the top of the jacket 324, a protrusion 324d is provided, and by pressing this protrusion 324d with a foot or the like, the upper electrode plate 322 is deformed through the protrusion 324d in the region of the space portion 323, resulting in a switching operation being performed by the lower electrode plate 321 and the upper electrode plate 322.
As stated above, conventional continuous-length switches are easy to be short-circuited, thereby presenting problems of safety and reliability, and requiring cumbersome secondary working. In addition, they have presented a problem in that power requirement is high.
The present invention has been developed in consideration of the above situation, being intended to offer a continuous-length switch which is excellent in safety and reliability, eliminates the need for a cumbersome secondary working, allows improvement of the operational efficiency during manufacturing, and can minimize the power requirement.
As stated above, conventional continuous-length switches are easy to be short-circuited, thereby presenting problems of safety and reliability. And to prevent the electrode plates from being buckled during transporting, storing and the like, they were required to have been handled in a cumbersome and inconvenient way.
The present invention has been developed in consideration of the above situation, being intended to offer a continuous-length switch which is difficult to be short-circuited and, is excellent in safety and reliability. Also, if winding up or the like of the switch is carried out, buckling and the like are difficult to be caused. Therefore, the restriction in handling the switch can be loosened, and winding the switch around a drum for transportation and storage is allowed, thereby resulting in the operability of the switch being improved and the space requirement therefor being reduced.
With the conventional continuous-length switch as stated above, a continuous-length jacket 324 is used to form a space portion 323 between the lower electrode plate 321 and the upper electrode plate 322. Then, the process of cross-winding the two strings 325 is carried out to integrate the lower electrode plate 321 with the upper electrode plate 322. Therefore, a problem in that the manufacturing process is cumbersome, which results in the cost of the continuous-length switch being increased, has been presented.
The present invention has been developed in consideration of the above situation, being intended to offer a continuous-length switch which is excellent in durability. A manufacturing method for the switch is simple, and therefore, the manufacturing cost can be reduced and a continuous-length switch excellent in durability can be obtained.
According to one aspect of the invention, the continuous-length switch is a continuous-length switch including a pair of continuous-length electrode plates that are contacted with or separated from each other for carrying out a switching operation, wherein at least one of the pair of electrode plates has a linear conductive portion continuing in a longitudinal direction thereof.
Because, at least one electrode plate has a linear conductive portion continuing in the longitudinal direction, a problem of the conductor getting beneath the insulator can be avoided. Also, if a tensile force is applied to the lead wire for connection to another device, the electrode plate will not be deformed or displaced, resulting in the safety and the reliability of the switch being improved. In addition, the lead wire can easily be drawn out to be worked, which results in operation man-hours being reduced.
Further, because a linear conductive portion is provided, the line length of the electrode plate is shortened, resulting in the electrode resistance thereof being decreased. And, when a four-wire type disconnection detection is carried out, the electric power requirement can be minimized.
The continuous-length switch according to a second aspect of the invention is a continuous-length switch according to the first aspect, wherein at least one of the pair of electrode plates has a number of protrusions which are formed at fixed intervals, extending from the linear conductive portion continuing in the longitudinal direction toward a contact surface of the other electrode plate, and also along a direction crossing the linear conductive portion.
Because the continuous-length switch is configured so that at least one of the pair of electrode plates has a number of protrusions which are formed at fixed intervals, extending from the linear conductive portion along the direction crossing the linear conductive portion, the mechanical strength of this electrode plate with respect to an external force is lowered, which allows a highly sensitive switch to be realized. Because the mechanical strength of the electrode plate can be lowered, a strong material can be adopted for use as the electrode plate.
The continuous-length switch according to a third aspect of the invention is a continuous-length switch according to the first aspect, wherein at least one of the pair of electrode plates has a number of comb-tooth-like protrusions which are formed on the linear conductive portion continuing in the longitudinal direction.
Because the continuous-length switch is configured so that at least one of the pair of electrode plates has a number of comb-tooth-like protrusions which are formed on the linear conductive portion continuing in the longitudinal direction, the mechanical strength of this electrode plate with respect to an external force is lowered, which allows a highly sensitive switch to be realized. Because the mechanical strength of the electrode plate can be lowered, a strong material can be adopted for use as the electrode.
The continuous-length switch according to a fourth aspect of the invention is a continuous-length switch including a pair of continuous-length electrode plates that are contacted with or separated from each other for carrying out a switching operation, wherein at least one of the pair of electrode plates has a linear conductive portion at both side areas thereof along the longitudinal direction of this electrode plate. Between both of these linear conductive portions, non-conductive portions having an optional geometry are formed.
Because at least one of the pair of electrode plates has a linear conductive portion at both side areas along the longitudinal direction, and because between both of these linear conductive portions non-conductive portions having an optional geometry are formed, a problem of the conductor getting beneath the insulator, as is encountered with conventional continuous-length switches, can be avoided. Also, if a tensile force is applied to the lead wire for connection to another device, this electrode plate will not be deformed or displaced, resulting in the safety and reliability of the switch being improved. In addition, the lead wire can easily be drawn out to be worked, which results in operation man-hours being reduced.
Further, because a linear conductive portion is provided at both side areas, and because between these linear conductive portions non-conductive portions having an optional geometry are formed, the conductive distance is smaller, resulting in the electrical resistance being reduced. And, even in the case where the four-wire type disconnection detection is performed, the power requirement can be minimized.
The continuous-length switch according to a fifth aspect of the invention is a continuous-length switch according to the fourth aspect, wherein the non-conductive portions are selected from circular holes, oval holes, rhombic holes, polygonal holes, lattice holes, and nearly step-like holes.
Because a continuous-length switch with which the geometry of the non-conductive portions can be specified to be any one of various geometries, such as circular holes, oval holes, rhombic holes, polygonal holes, lattice holes, and nearly step-like holes, an optional geometry of the non-conductive portions can be selected to reduce the conductive distance, decrease the electrical resistance, and minimize the power requirement even in the case where the four-wire type disconnection detection is performed.
The continuous-length switch according to a sixth aspect of the invention is a continuous-length switch according to the fourth aspect, wherein the non-conductive portions are a number of variation holes which are defined by a number of bridges interconnecting the linear conductive portions. The bridges have a bulging portion at a middle thereof and are spaced from adjacent bridges.
According to the sixth aspect, as is the case with the invention as set forth in the fifth aspect, a continuous-length switch is provided for which the conductive distance can be reduced, the electrical resistance can be decreased, and the power requirement can be minimized even in the case where the four-wire type disconnection detection is performed.
The continuous-length switch according to a seventh aspect of the invention is a continuous-length switch in which a pair of continuous-length electrode plates are contacted with or separated from each other for carrying out switching operation, wherein at least one of the pair of electrode plates has linear conductive portions formed at both side areas thereof along the longitudinal direction of this electrode plate, non-conductive portions which are formed between the linear conductive portions and comprise holes having an optional geometry of various polygonal geometries or various geometries other than the polygonal geometries, and protrusions formed at the locations of the linear conductive portions outside of each of the holes.
Because at least one of the pair of electrode plates is configured so that linear conductive portions are formed at both side areas along the longitudinal direction, because non-conductive portions comprising holes having an optional geometry of various geometries are formed between the linear conductive portions and because protrusions are formed at the locations of the linear conductive portions outside of each of the holes, the linear conductive portions allow the avoidance of a problem of the conductor getting beneath the insulator, as is encountered with conventional continuous-length switches, to prevent occurrence of short-circuiting. Also provided is excellent safety and reliability, and the difference between the inside and outside diameters of the continuous-length switch which is generated during bending can be accommodated by the protrusions, which allows the continuous-length switch to be easily wound around a drum or the like with generation of buckling of the electrode plate being suppressed. Therefore, improvement of operability of the switch and reduction of a space requirement can be achieved.
The continuous-length switch according to an eighth aspect of the invention is a continuous-length switch including a pair of continuous-length electrode plates that are contacted with or separated from each other for carrying out a switching operation, wherein at least one of the pair of electrode plates has linear conductive portions formed at both side areas along the longitudinal direction of this electrode plate, non-conductive portions which are formed between the linear conductive portions which comprise holes having an optional geometry of various polygonal geometries and various geometries other than the polygonal geometries, and protrusions which have a sectional geometry selected from various polygonal geometries and various geometries other than the polygonal geometries, including triangular, trapezoidal, circular, semi-circular, and oval geometries, being formed at the locations of the linear conductive portions outside of each of the holes.
According to the eighth aspect, at least one of the pair of electrode plates is configured so that linear conductive portions are formed at both side areas along the longitudinal direction, non-conductive portions comprising holes having an optional geometry of the various geometries are formed between both of the linear conductive portions, and protrusions which have a sectional geometry selected from the various polygonal geometries and various geometries other than the polygonal geometries, including triangular, trapezoidal, circular, semi-circular, and oval geometries are formed at the locations of the linear conductive portions outside of each of the holes.
Therefore, as is the case with the invention according to die seventh embodiment, the linear conductive portions allow the avoidance of a problem of the conductor getting beneath the insulator, as is encountered with conventional continuous-length switches, to prevent occurrence of short-circuiting. Also, provided is excellent safety and reliability, and the difference between the inside and outside diameters of the continuous-length switch itself which is generated during bending can be accommodated by the protrusions having any one of the above-mentioned geometries, which allows the continuous-length switch to be easily wound around a drum or the like with generation of buckling of the electrode plate being suppressed. Therefore, improvement of operability of the switch and reduction of a space requirement can be achieved.
The continuous-length switch according to a ninth aspect of the invention is a continuous-length switch comprising: a lower electrode plate made of a continuous-length plate-like conductive material; a continuous-length insulating material which covers the circumference of this lower electrode plate except at an opening portion of the insulating material; an upper electrode plate made of a continuous-length plate-like conductive material which is placed on the opening portion; and a jacket made of a continuous-length insulating material which covers the circumferences of the insulating material and the upper electrode plate, wherein the jacket has a protrusion at its top.
Because the lower electrode plate is covered with a continuous-length insulating material except for at the opening portion, and because the circumferences of the insulating material and the upper electrode plate are covered with a jacket which is made of a continuous-length insulating material that has a protrusion at its top, the lower electrode plate and the tipper electrode plate can be firmly held in place while the opening portion provides a space region for contact that is formed between the lower electrode plate and the upper electrode plate, whereby a continuous-length switch having excellent durability can be provided.
A method for manufacturing a continuous-length switch comprises a process in which the circumference of a lower electrode plate that is made of a continuous-length plate-like conductive material is covered with an insulating material of a uniform thickness by extrusion; a process in which two grooves are formed parallel to each other in the insulating material above the lower electrode plate along the longitudinal direction of the lower electrode plate; a process in which the insulating material on the upper side of the lower electrode plate is peeled off in the area between the two grooves along the longitudinal direction of the lower electrode plate to form an opening portion on the upper side of the lower electrode plate; a process in which an upper electrode plate made of a continuous-length plate-like conductive material is placed on the insulating material over the opening portion; and a process in which a jacket having a protrusion at a middle of the top thereof, which extends along the longitudinal direction, is formed over the entire circumferences of the insulating material and the upper electrode plate by extrusion-forming an insulating material.
Because the circumference of the lower electrode plate made of a continuous-length plate-like conductive material is covered with an insulating material of a uniform thickness by extrusion; because two grooves are formed in the insulating material; because the insulating material is peeled off in the area between the two grooves along the longitudinal direction of the lower electrode plate to form an opening portion on the upper side of the lower electrode plate; because an upper electrode plate made of a continuous-length plate-like conductive material is placed on the insulating material over the opening portion; and because a jacket having a protrusion at the middle of the top thereof is formed over the entire circumferences of the insulating material and the upper electrode plate by extrusion-forming an insulating material to provide a continuous-length switch, the manufacturing process can be simplified as compared to that for the conventional continuous-length switch, while the manufacturing cost is reduced. Thus, a manufacturing method which allows for the obtaining of a continuous-length switch having excellent durability can be realized.